Because you can&#39;t use the presence validation on boolean fields. Use inclusion instead. See the documentation here: http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html

&gt; If you want to validate the presence of a boolean field (where the real values are true and false), you will want to use validates_inclusion_of :field_name, in: [true, false].)

If I have a dataframe with multiple columns `[&#39;x&#39;, &#39;y&#39;, &#39;z&#39;]`, how do I forward fill only one column `&#39;x&#39;`? Or a group of columns `[&#39;x&#39;,&#39;y&#39;]`?

I only know how to do it by axis.



forward fill specific columns in pandas dataframe

I&#39;m trying to get data from a zipped csv file. Is there a way to do this without unzipping the whole files? If not, how can I unzip the files and read them efficiently?

Reading csv zipped files in python

So, I have a form, using a boolean to select male or female. When i use validates :presense for the boolean fields, it returns back, gender cannot be blank! Wehn I remove the validates portion, it lets it pass through as true or false into the DB. It doesn&#39;t leave it nil. I&#39;m assuming this is an issue because im using t/f but I can&#39;t seem to figure out why. Here is my model

    class Visit &lt; ActiveRecord::Base
        validates :user_id, :first_name, :last_name, :birthdate, :gender, 
            presence: true
    end

And my view for the field

    &lt;%= f.select :gender, 
        [[&#39;Male&#39;,false],[&#39;Female&#39;,true]], :value =&gt; false,
        label: &quot;Gender&quot; %&gt;





Rails validates_presense not validating on boolean?

So, I have a form, using a boolean to select male or female. When i use validates :presense for the boolean fields, it returns back, gender cannot be blank! Wehn I remove the validates portion, it lets it pass through as true or false into the DB. It doesn't leave it nil. I'm assuming this is an issue because im using t/f but I can't seem to figure out why. Here is my model
<pre><code class="hljs language-ruby">class Visit &#x3C; ActiveRecord::Base
 validates :user_id, :first_name, :last_name, :birthdate, :gender, 
 presence: true
end
</code></pre>
And my view for the field
<pre><code class="hljs language-lua">&#x3C;%= f.select :gender, 
 [['Male',false],['Female',true]], :value => false,
 label: "Gender" %>
</code></pre>

Let&#39;s say that I have a `User` model with attributes `:id, :first_name, :last_name, and :email`. In my application, guest users shouldn&#39;t see `User&#39;s email and last_name`. I know how to select specific values if I want a list of users but I don&#39;t know how I can get specific attributes of a specific user like 

    User.find_by(id: 5).select(:id, :first_name).

One solution to that is to user

    User.find_by(id: 5).attributes.slice(&#39;id&#39;, &#39;first_name&#39;) 

but then I get a hash instead of an AR record. I could do

    User.select(:id, :first_name).find_by(id: 1) 

but the thing that I don&#39;t know which filters I should filter since I need to know the user first.

Could you help me?

Get specific attributes from an ActiveRecord model

I am building a blog app.  I&#39;d like to be able to pluralize the word &quot;article&quot; if more than one &quot;post&quot; is &quot;published.&quot;

Like so:
Available Articles
or
Available Article

This is what I have....


     Available &lt;%=  pluralize @posts.published, &quot;Article&quot; %&gt;:


I&#39;ve tried

     Available &lt;%=  pluralize @posts.published.count, &quot;Article&quot; %&gt;:

and that works...but I don&#39;t want the number.  It shouldn&#39;t read Available 5 Articles....it should have no number.

pluralize without count number in rails 4

Following this tutorial [[link][1]] to install gitlab on a dedicated server. I need to :

    sudo -u git -H bundle install --deployment --without development test postgres aws

But an error occurred while installing rugged :

    Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
    
        /usr/local/bin/ruby extconf.rb
    checking for cmake... no
    ERROR: CMake is required to build Rugged.
    *** extconf.rb failed ***
    Could not create Makefile due to some reason, probably lack of necessary
    libraries and/or headers.  Check the mkmf.log file for more details.  You may
    need configuration options.
    
    Provided configuration options:
    	--with-opt-dir
    	--without-opt-dir
    	--with-opt-include
    	--without-opt-include=${opt-dir}/include
    	--with-opt-lib
    	--without-opt-lib=${opt-dir}/lib
    	--with-make-prog
    	--without-make-prog
    	--srcdir=.
    	--curdir
    	--ruby=/usr/local/bin/ruby
    
    
        Gem files will remain installed in /home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/rugged-0.21.2 for inspection.
        Results logged to /home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/rugged-0.21.2/ext/rugged/gem_make.out
        An error occurred while installing rugged (0.21.2), and Bundler cannot continue.
        Make sure that `gem install rugged -v &#39;0.21.2&#39;` succeeds before bundling.

So I installed rugged -&gt; I installed CMake &amp; config-pkg :

    /home/git/gitlab$ sudo gem install rugged
    Building native extensions.  This could take a while...
    Successfully installed rugged-0.21.2
    Parsing documentation for rugged-0.21.2
    unable to convert &quot;\xC0&quot; from ASCII-8BIT to UTF-8 for lib/rugged/rugged.so, skipping
    1 gem installed

But it doesnt change anything : 

    Errno::EACCES: Permission denied - /home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/rugged-0.21.2/LICENSE
    An error occurred while installing rugged (0.21.2), and Bundler cannot continue.
    Make sure that `gem install rugged -v &#39;0.21.2&#39;` succeeds before bundling.

Any idea ?


  [1]: http://blog.bobbyallen.me/2014/01/11/setup-your-own-private-github-server-using-gitlab-and-ubuntu-server-12-04-lts/

An error occurred while installing rugged

Referencing to Rails 4.2 [add_foreign_key][1] support:

        # add a foreign key to `articles.author_id` referencing `authors.id`
        add_foreign_key :articles, :authors

How to create a nullable foreign key constraint, to allow the situation, where `articles.author_id` can be sometimes null?

  [1]: http://edgeguides.rubyonrails.org/4_2_release_notes.html#foreign-key-support

Add nullable foreign key in Rails

trying to upgrade to Rails 4.2, using delayed_job_active_record. I&#39;ve not set the delayed_job backend for test environment as thought that way jobs would execute straight away. 

I&#39;m trying to test the new &#39;deliver_later&#39; method with RSpec, but I&#39;m not sure how.

Old controller code:

    ServiceMailer.delay.new_user(@user)

New controller code:

    ServiceMailer.new_user(@user).deliver_later

I USED to test it like so:

    expect(ServiceMailer).to receive(:new_user).with(@user).and_return(double(&quot;mailer&quot;, :deliver =&gt; true))

Now I get errors using that. (Double &quot;mailer&quot; received unexpected message :deliver_later with (no args))

Just

    expect(ServiceMailer).to receive(:new_user)

fails too with &#39;undefined method `deliver_later&#39; for nil:NilClass&#39;

I&#39;ve tried some examples that allow you to see if jobs are enqueued using test_helper in ActiveJob but I haven&#39;t managed to test that the correct job is queued.

    expect(enqueued_jobs.size).to eq(1)

This passes if the test_helper is included, but it doesn&#39;t allow me to check it is the correct email that is being sent.

What I want to do is:

 - test that the correct email is queued (or executed straight away in test env)
 - with the correct parameters (@user)

Any ideas??
thanks

How to test ActionMailer deliver_later with rspec

I have 2 models as describes below.

    class EmpGroup &lt; ActiveRecord::Base
      belongs_to :user
      has_many :emp_group_members, dependent: :destroy
    end


and 

    class EmpGroupMember &lt; ActiveRecord::Base
      belongs_to :emp_group
      belongs_to :user
    end

now the problem is whenever I tried to destroy a group then I received a error as below.

    PG::ForeignKeyViolation: ERROR:  update or delete on table &quot;emp_groups&quot; violates foreign key constraint &quot;fk_rails_bd68440021&quot; on table &quot;emp_group_members&quot;
    DETAIL:  Key (id)=(1) is still referenced from table &quot;emp_group_members&quot;.

What I&#39;m missing?

Rails: How to use dependent: :destroy in rails?

I&#39;m pretty sure the error has nothing to do with the actual content of the `TenantIdLoader` module. Instead, it has something to do with `ActiveSupport` Dependencies.

I can&#39;t seem to get past this error. From what I&#39;ve read, it&#39;s because either `ActiveRecord::Base` is getting reloaded or `Company::TenantIdLoader` is getting reloaded, and it&#39;s somehow not communicating that. Help, please! I&#39;d really like to be able to get upgraded to Rails 4.2.

# EDIT

I&#39;ve now learned that it&#39;s because I&#39;m referencing `Tenant` which is getting reloaded automatically. I need to be able to actually reference the class though, so does anyone know how to get around this?



config/application.rb

    config.autoload_paths += %W( #{config.root}/lib/company )


config/initializers/company.rb

    ActionMailer::Base.send(:include, Company::TenantIdLoader)

lib/company/tenant_id_loader.rb

    module Company
      module TenantIdLoader
    
        extend ActiveSupport::Concern
    
        included do
          cattr_accessor :tenant_dependency
          self.tenant_dependency = {}
      
          after_initialize do
            self.tenant_id = Tenant.active.id if self.class.tenant_dependent? and self.new_record? and Tenant.active.present? and !Tenant.active.zero?
          end
        end
    
        # class methods to be mixed in
        module ClassMethods
      
          # returns true if this model&#39;s table has a tenant_id
          def tenant_dependent?
            self.tenant_dependency[self.table_name] ||= self.column_names.include?(&#39;tenant_id&#39;)
          end
      
        end
    
      end
    end


A copy of xxx has been removed from the module tree but is still active

In Rails, both [find_each][1] and [where][2] are used for retrieving data from Database supported by ActiveRecord.

You can pass your query condition to `where`, like:

    c = Category.where(:name =&gt; &#39;Ruby&#39;, :position =&gt; 1)

And you can pass batch size to `find_each`, like:

    Hedgehog.find_each(batch_size: 50).map{ |p| p.to_json }

But what&#39;s the difference between the following 2 code?

    # code 1
    Person.where(&quot;age &gt; 21&quot;).find_each(batch_size: 50) do |person|
      # processing
    end

    # code 2
    Person.where(&quot;age &gt; 21&quot;).each do |person|
      # processing
    end

Does code 1 batch retrieve 50 tuples each time, and code 2 retrieve all tuples in one time? More details explaination is welcomed.

My opinion is:

 1. both `where` and `find_each` can be used for batch retrieving, but user can define batch size when using `find_each`.
 2. `find_each` does not support passing query condition.

Please correct me if my understanding is wrong.

  [1]: http://apidock.com/rails/v4.2.1/ActiveRecord/Batches/find_each
  [2]: http://apidock.com/rails/v4.2.1/ActiveRecord/QueryMethods/where

In Rails, what&#39;s the difference between find_each and where?

It is standard convention to use `if foo is None` rather than `if foo == None` to test if a value is specifically `None`.

If you want to determine whether a value is exactly `True` (not just a true-like value), is there any reason to use `if foo == True` rather than `if foo is True`? Does this vary between implementations such as CPython (2.x and 3.x), Jython, PyPy, etc.?

Example: say `True` is used as a singleton value that you want to differentiate from the value `&#39;bar&#39;`, or any other true-like value:

    if foo is True: # vs foo == True
        ...
    elif foo == &#39;bar&#39;:
        ...

Is there a case where using `if foo is True` would yield different results from `if foo == True`?


NOTE: I am aware of [Python booleans - if x:, vs if x == True, vs if x is True][1]. However, it only addresses whether `if foo`, `if foo == True`, or `if foo is True` should generally be used to determine whether `foo` has a true-like value.



---

UPDATE: According to [PEP 285][2] &#167; Specification:

&gt; The values False and True will be singletons, like None.


  [1]: https://stackoverflow.com/q/20420934/369450
  [2]: https://www.python.org/dev/peps/pep-0285

Boolean identity == True vs is True

I know that `null` is an object with no attributes or functions.

However, I am confused that why `console.log(null == false);` and `console.log(null == true);` both return false.

What are the conversion rules between `null` and `boolean`?

Why (null == false) and (null == true) both return false?

Is there an API to convert most possible String representations of Boolean values (e.g. &quot;True&quot;, &quot;true&quot;, &quot;False&quot;, &quot;false&quot;, &quot;yes&quot;, &quot;no&quot;, &quot;1&quot;, &quot;0&quot;) into a Bool in Swift?

If not, what would be the most Swift-like approach to coding this from scratch? Would it be a functional map() operation? Or something else?

The original source data in this instance is JSON, but I&#39;m interested in the crux of solving the problem in the most Swift-like way possible and hence learning more about the language in the process.

Convert String to Bool in Swift - via API or most Swift-like approach

So I tried the &quot;evil&quot; thing Ned Deily mentioned in his answer [here][1]. Now I have that the type True is now always False. How would I reverse this within the interactive window?

Thing to not do:

    True = False

Since True has now been completely overridden with False, there doesn&#39;t seem to be an obvious way to back-track. Is there a module that True comes from that I can do something like:

    True = &lt;&#39;module&#39;&gt;.True


  [1]: https://stackoverflow.com/questions/12765833/counting-the-number-of-true-booleans-in-a-python-list/12766000#12766000

How do I undo True = False in python interactive mode?

Is there a more compact or pythonic way to write the boolean expression

    a + b == c or a + c == b or b + c == a

I came up with 

    a + b + c in (2*a, 2*b, 2*c)

but that is a little strange.

Content Type	Original Author	Original Content on Stackoverflow
Question	keith	View Question on Stackoverflow
Solution 1 - Ruby on-Rails	Lukas Eklund	View Answer on Stackoverflow

Rails validates_presense not validating on boolean?

Ruby on-Rails Problem Overview

Ruby on-Rails Solutions

Solution 1 - Ruby on-Rails

Reading csv zipped files in python

forward fill specific columns in pandas dataframe

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